1. Field of the Invention
The present invention relates to an electronic chip component having a package in which at least a portion thereof is made of a resin molding and external electrodes are provided on the surface of the package.
2. Description of the Related Art
In order to increase the packaging density of a substrate in an electronic apparatus required by advances in miniaturization of electronic devices in general, electronic chip components that are mounted on the surface of a circuit board are widely used as electronic components. This type of electronic chip component mainly uses a ceramic package in order to ensure heat resistance to reflow soldering. External electrodes that are provided on the surface of the package are formed by baking thick-film silver to define a base, at sufficiently high temperatures (about 800xc2x0 C.), and then plating the silver thereon.
However, such a ceramic package has drawbacks of having high material cost, difficulties in molding a complicated shape, the need for polishing such as lapping or the like to achieve thinning, high production cost, and other drawbacks. Thick-film silver which is baked at high temperature has the drawback of requiring a dedicated burning furnace, and so there is reduction in production efficiency. Therefore, this type of thick-film film silver cannot be applied to electronic components that have a portion that is weak against high-temperature thermal stress.
In order to solve the above problems, an external electrode is provided with a base electrode made of conductive paste of the type which is baked at low temperature, and a metal plate electrode provided on the surface of the base electrode (Japanese Unexamined Patent Publication No. 3-175711). In this case, the base electrode is baked at low temperatures (for example, about 200xc2x0 C. or less) with low thermal stress when forming the external electrode, thereby having the advantage of permitting a wide range of applications.
However, in the use of conductive paste of the type which is baked at low temperature for forming the base electrode, in many cases, the base electrode cannot resist thermal stress caused during reflow soldering. This is because heat up to a temperature of about 250xc2x0 C. is applied in reflow soldering, and thus, the base electrode is thermally deformed by this heat which causes cracks or separation in the base electrode.
To overcome the problems described above, preferred embodiments of the present invention provide an electronic chip component including a package, at least a portion of the package being made of a heat-resistant resin molding, and an external electrode provided on a surface of the resin molding, wherein the resin molding includes a polymeric material having polar groups of at least one of an ether group, an ester group, a hydroxyl group, a carbonyl group, an amido group, and an imido group, and the external electrode has a multilayered structure including at least two layers including a lowermost layer having a conductive film made of baked conductive paste including a resin composition and metal particles, and an uppermost layer including a metal plate having good solderability, the resin composition including a compound having a trifunctional or higher functional epoxy group in at least one molecule.
In another preferred embodiment of the present invention, an electronic chip component includes a package, at least a portion of the package is made of a heat-resistant resin molding, and an external electrode provided on a surface of the resin molding, wherein the resin molding includes a polymeric material having polar groups, and the external electrode has a multilayered structure having at least two layers which include a lowermost layer having a conductive film containing a resin composition and metal particles, the resin molding containing a compound having a trifunctional or higher functional epoxy group in at least one molecule.
In another preferred embodiment of the present invention, a method of manufacturing an electronic chip component includes the steps of providing a package having at least a portion of which is made of a heat-resistant resin molding such as a polymeric material having polar groups of at least one of an ether group, an ester group, a hydroxyl group, a carbonyl group, an amido group, and an imido group, and forming an external electrode having at least two layers, wherein a lowermost layer of the external electrode is formed on a surface of the resin molding by baking a conductive paste made of a resin composition and metal particles, wherein the resin composition includes a compound having a trifunctional or higher functional epoxy group in at least one molecule.
In preferred embodiments of the present invention, the resin molding provides greater heat resistance while the polymeric materials having the polar groups provide greater adhesion with the lowermost layer of the external electrode because the conductive paste is made of a resin composition and metal particles, especially when the resin composition is made of a trifunctional or higher functional epoxy group.
Other features, elements and advantages of the present invention will be described in detail below with reference to preferred embodiments of the present invention and the attached drawings.